Process for developing silver halide and compositions therefor



Feb. 21, 1967 Q ESTER ETAL 3,305,362

PROCESS FOR DEVELOPING SILVER HALIDE AND COMPOSITIONS THEREFOR Filed Feb. 26, 1963 2 R 4 6 min.

' INVENTORS. OSKAF? R/ESTER WERNER STRACKE BY (4M 6.. L K M V (K ATTORNEY5 United States Patent 3,305,362 PROCES lFQR DEVELGPING SlllLVER HALIDE AND CGMPUMTIONS THEREFOR Oslrar Riester and Werner Straclre, Leverlrusen, Germany,

assignors to Agfa Airtiengesellschaft, Leverinlsen, Germany, a corporation of Germany Filed Feb. 26, 1963, Ser. No. 260,998 Claims priority, application Germany, Mar. 8, 1962, A. $9,654 21 Claims. (Cl. 96-66) This invention relates to photographic emulsions, respectively to light-sensitive layers produced of the said emulsions which are improved with respect to their stability by the use of novel stabilizers.

It is known that silver halide emulsions show a more or less marked tendency to fogging during storage. The same phenomenon also occurs with photographic layers cast from these emulsions, so that such layers become unsuitable for use after a certain period of time. This fog formation is in particular deleterious in connection with photographic papers, since even the slightest degree of fogging is very noticeable with such papers.

Accordingly, considerable research has already been made to find substances which prevent fogging. A number of organic compounds, such as Z-mercaptobenzthiazole, nitrobenzimidazole, and benztriazole are elfective in this direction. Such substances are known as stabilizers. However, this undoubted advantage is compensated by a number of disadvantages, which restrict the use of such substances. For example, the photographic light sensitivity is reduced by such additions or the gradation is adversely affected. Other substances of this type cause a displacement of the colour tone.

It is an object of the present invention to overcome the disadvantages referred to above and to provide photographic emulsions which have no propensity to the formation of fog and which have improved keeping qualities.

Another object is to provide new stabilizers having excellent stabilizing properties without concomitant decreases in sensitivity or displacement of the colour tone of the developed silver image or without deleterious influence on the gradation.

The objects can be attained by processing the photographic material in the presence of stabilizers of the following formula:

in which Z represents an oxygen, sulphur or selenium atom and Y represents the carbon atom necessary for completing a S-membered or 6-membered ring, the said atoms at the same time constituting ring members of an aromatic system which consists of one or two condensed benzene rings having an acid substituent, such as a carboxyl group, a sulpho group or sulphonamide group.

The organic system, for example, a benzene or naphthalene ring, can in its turn contain other substituents, but these generally have no influence on the activity of the class of compounds according to the invention. Such substituents include for example halogen atoms and alkyl, ether and ester groups, containing preferably up to carbon atoms.

The sulphonamide group can in its turn also be substituted by alkyl, aralkyl or aryl radicals. The compounds according to the invention can be used with all usual silver halide emulsions. Their eifect is particularly advantageous with silver chlorobromide emulsions, such as described by way of example in the Bios-Final-Report 3,305,302 Patented Feb. 21, 1967 "ice 252, under the names Brovira-braun, Portriga kralftig, Lupex normalbraun, etc. The silver chlorobromide emulsions may contain silver iodide up to 10 mol percent. The optimal concentration for use may -be determined in each particular case without difficulties. The quantities set out below may in general be used:

2100.l0 mol per mol of silver halide, advantageously 6-30.1O mol per mol of silver halide, or 20-500 mg. per litre of developer solution.

The superiority of the stabilizer according to the invention is particularly apparent under extreme conditions such as prolonged development periods or raising of the temperature of the developer. The substances according to the invention can be used in the form of the free acids or as salts, for example, of sodium, potassium or barium, or of an organic base. The substances are dissolved in a solvent which is compatible with the emulsion, such as water or methanol. The stabilizers can also be added to another layer. The stabilizers can also be used in the development baths or in a preliminary bath, in order to achieve the same effect and in order to develop already slightly fogged photographic layers with a substantially smaller degree of fogging.

The activity of the stabilizers according to the invention is generally not influenced by other emulsion additives such as sensitizers, wetting agents of natural or synthetic origin, hardeners, etc.

The stabilizers according to the invention can be used in black and white and-colour photographic materials, containing colour couplers capable of reacting with the oxidation product of a primary aromatic amine developer to form a dye.

Example 1 To a silver chlorobromide emulsion, which has, for example, been prepared ac-cording to Bios-Berichte, Final Report 252, Item No. 9, Brovira Normal Braun, the sodium salt of 2'mercapto-[naphtho-l,2:4,5-oxazole]-sulphonic acid-(4) (Formula 1) is added before casting in the form of an aqueous methanolic solution and in a dilution of 121000. The reduction in the fogging obtained is apparent from the following table:

A developer of the following composition is used:

Metol g 1 Sodiumsulfit sicc. g 13 Hydroquinone g 3 Sodium carbonate sicc. g 26 Potassium bromide g 1 Water cc-m 1000 The sensitometric threshold sensitivity is the same with all four samples. The superiority of the new stabilizer is apparent from the fogging values, the gradation only being slightly changed, whereas the 7 value is much more strongly lowered by the standard stabilizer 2-mercapto-5- 3 phenylamino-thiodiazole and assumes values completely unsuitable for use when the quantity of stabilizer is in= creased.

The aforesaid oxazole derivative is prepared in the following manner:

480 g. of 1-amino-2-oxynaphthalene-4-sulphonic acid are dissolved in a solution of 180 g. of caustic soda in 500 ml. of water. After adding 2 litres of methanol and 150 ml. of carbon disulphide, the mixture is heated for 4 /2 hours under reflux to boiling point. The product precipitated after cooling, is recrystallized from water with addition of active carbon. The sodium salt is obtained as colourless crystals containing one molecule of water of crystallisation.

Example 2 80 mg. of the sodium salt of Z-mercapto-(naphtho- 2,3;4,5-oxazole-(7)-sulphonic acid-(6') in the form of a 1% solution in water (Formula II) are added to 1 litre of a silver chlorobromide emulsion ready for casting. A photographic paper coated therewith shows a reduction in fogging, even with considerably extended development times.

The results of the measurements are evaluated in FIG- URES 1 and 2. In these graphs, the development time is plotted as abscissae against the density of the fogging as ordinates. FIGURE 1 relates to experiments which are carried out at room temperature, while FIGURE 2 illustrates the behaviour of an emulsion which has been stored for 2 days at 60 C. in a heating chamber.

Curve 1 applies to the emulsion without stabilizer, curve 2 to an emulsion with a standard stabilizer and curve 3 to an emulsion which contains the aforementioned stabilizer according to the invention.

Z-mercapto-5-phenylaminothiodiazole standard stabilizer.

The oxazole of Formula II was prepared in the manner described in Example 1, starting from 2-amino-3-0xynaphthalene-6-sulphonic acid, the sodium salt being obtained as colourless needle-shaped crystals.

was used as Example 3 30 mg. of the sodium salt of 2-mercapto-6,7-benzobenzoxazole-S-sulphonic acid as a 1% aqueous solution (Formula III are added) to 1 litre of the emulsion ready for casting. After the photographic layer prepared therewith has been kept for 7 days in a heating chamber or oven at 40 C., it shows a fogging of 0.093 and a y=2.6, whereas the same emulsion with the standard stabiliser 2- mercapto-S-phenylaminothiodiazole has a fogging value of 0.095 and a gradation of 2.3. Without stabilizer, the fogging value is 0.22 1 and :2.6.

The Formula III compound is prepared by reacting 1- oxy-2-aminonaphthalene-4-sulphonic acid with carbon disulphide in the manner previously described. The sodium salt is obtained as colourless crystals containing 1 mol of water of crystallization.

Example 4 Fogging Gradation 7 Emulsion without stabilizer 0. 196 2. 75 Emulsion plus standard stabilizer 0.130 2. 25 Emulsion plus stabilizer Formula IV 0. 124 2. 75

1-amino-2-oxynaphthalene-6-sulphonic acid is used for the preparation of the stabilizer, of Formula IV and the preparation is carried out as indicated in Example 1. The sodium salt+1 mol of water of crystallisation is obtained.

4. Z-mercapto-S-phenylaminothiodiazole standard stabilizer.

was used as Example 5 An aqueous solution of the sodium salt of 2-mercapto- (perioxazinsulfonic acid-(8)) (Formula V) used as a stabilizer gives the following results with specimens subjected to the heating chamber test referred to above.

Fogging Gradation 7 Without stabilizer 0. 106 2.75 Plus 30 mg. of stabilizer according to Formula V 0. 144 2. 75 Plus mg. of stabilizer according to Formula V 0. 003 2.75 Plus 100 mg. of stabilizer according to Formula V 0. 070 3.

The stabilizer is prepared according to the method indicated in Example 4 from 1-amino-8-oxynaphthalene-o-sulphonic acid. Colourless crystals are obtained.

Example 6 Example 7 The addition of the sodium salt of 2-mercapto(naphtho- 2',3',:4,5-oxazole)-disulphonic acid (6',8) (Formula VII) reduces the fogging in the following manner when the development time is extended to 10 minutes:

Fogging Emulsion without additive 0.138 Emulsion plus 30 mg. of stabilizer according to Formula VII 0.099 Emulsion plus 60 mg. of stabilizer according to Formula VII 0.083

The gradation is practically the same in all cases ('y=2.6). The stabilizer is prepared from 2-oxy-3-aminonaphthalene 5,7-disulphonic acid in the manner described. The disodium salt, which crystallizes with 3 mols of water, is obtained as colourless crystals.

Example 8 30 mg. of the sodium salt of Z-mercapto-S-chlorobenzoxazole-7-sulphonic acid per litre of a gelatine-silver chlorobromide emulsion produces a reduction in fogging with a development time of 10 minutes from 0.095 to 0.051. The stabilizer (Formula VIII) is prepared in the manner indicated from 2-amino-4-chlorophenol-6-sulphonic acid. Colourless crystals of the sodium salt are obtained which are readily soluble in water.

Example 9 45 mg. of sodium salt of Z-mercaptobenzoxazole-S- sulphonic acid per litre of a normal silver bromide emulsion produced a reduction in the fogging from 0.095 to 0.064 when a development time of 10 minutes was employed.

The stabilizer (Formula IX) is prepared from 2-aminophenol-4-sulphonic acid in the manner described. Colourless crystals of the sodium salt, containing /2 mol of water are obtained.

Example Fogging after 7 l0 development Emulsion without additive Emulsion with 30 mg. of standard stabilizer.

Emulsion with 45 mg. of stabilizer according to Formula X Z-mercaptobenzthiazole was used as standard stabilizer. Stabilizer X was prepared as follows:

175 g. of sodium salt of 2-nitrochlorobenzene-4-sulphonic acid are slowly added with stirring to a solution consisting of 130 g. of sodium sulphide in 500 ml. of water at a temperature of 60 C. The temperature of the solution rises to boiling point point because of the heat of reaction.

60 ml. of carbon disulphide are then added and the mixture heated for another 2 hours under reflux. The pH of the reaction solution is adjusted to 3 with concentrated hydrochloride acid. The product which precipitates is dissolved after suction-filtering, in dilute sodium hydroxide solution. The resulting solution is clarified with active carbon and precipitation is again effected by adding dilute hydrochloric acid to give a pH of 3. The precipitate is washed with a little water and isopropanol. Colourless crystals of the sodium salt +1 mol of water of crystallisation are obtained.

Example 11 Example 12 2 mercaptobenzoxazole 5 carboxylic acid (Formula XII) produces the following fogging values in a silver chlorobromide emulsion which has been heated for 7 days in an oven at 40 C.

Fogging Gradation y Emulsion without additive Emulsion mg. of standard stabilized.

Emulsion +45 mg. of stabilizer according to Formula XII The stabilizer according to Formula XII is prepared from 3-amino-4-hydroxybenzoic acid in the manner described.

Example 13 45 mg. of Z-mercaptobenzoxazole-7-carboxylic acid (XIII) per litre of emulsion produce a fogging of 0.052 and a gradation in the experiments indicated in Example 12. It is prepared from 2-hydroxy-3-aminobenzoic acid, the sodium salt containing /2 mol of water crystallisation being obtained.

- Example 14 60 mg. of the sodium salt of Z-mercapto-S-sulphonamido-benzoxazole (XIV) produce, in the aforementioned emulsion, the following values after the layer produced therewith has been kept for 7 days at 40 C.

Fogging Emulsion without additive 0.079

Emulsion plus 20 mg. of standard stabilizer 0.046 Emulsion plus mg. of stabilizer acccording to Formula XIV 0.038

The stabilizer is prepared from l-hydroxy-Z-aminobenzene-4-sulphonic acid amide in the manner described and the sodium salt is obtained in the form of colourless crystals.

Example 15 60 mg. of the sodium salt of 2-merca-pto-6-sulphonamidobenzoxazole produce a fogging of 0.044 in the series of experiments described in Example 14. The stabilizer is prepared from 1-hydroxy-2-aminobenzene-S-sulphonamide and the sodium salt is obtained.

Example 16 45 mg. of the sodium salt of 2-mercapto-S-methyl-benzoxazole-7-sulphonic acid produce the following fogging values after 10 minutes development:

Emulsion without additive 0.074 Emulsion plus standard stabilizer 0.057 Emulsion plus stabilizer according to Formula XVI 0.047

The stabilizer is prepared from 1-oxy-2-amino-4-methylbe-nzene-6-sulphonic acid in the manner described and the sodium salt containing /z mol of Water is obtained.

Example 17 The stabilizers can be applied in admixture with other stabilizers according to the invention or with other known stabilizers.

The following tables show the results of tests with mixtures of stabilizers. The stabilizers were added in the form of an aqueous solution to a silver chlorobromide emulsion.

Fogging after 10 mins.

Emulsion: development Without stabilizer 0.273 Plus 40 mg./l. stabilizer II 0.133 Plus 20 mg./l. stabilizer II and IV each 0.138 Plus 20 mg./l. stabilizer II and I each 0.122 Plus 20 g. standard stabilizer (compare Example 2) 0.160

Fogging after 10 mins.

Emulsion: development Without stabilizer 0.287 Plus 10 mg./l. standard stabilizer (compare Example 2) 0.193 Plus 20 mg./l.- standard stabilizer (comp-are Example 2) 0.168 Plus 10 mg./l. standard stabilizer plus 20 m'g./l.

stabilizer II 0.159 Plus 15 mg./l. standard stabilizer plus 20 mg./l. stabilizer II 0.136 Plus 5 mg./l. standard stabilizer plus 40 mg./l.

stabilizer II 0.132

Similar results are obtained with the stabilizers according to Formulae XVII-XXIII. The said stabilizers are prepared as follows:

Compound X VII .--2 mercapto 5 (methylaminosulphor1)-benzthiazole is prepared from l-chloro-2-nitro-4- (methylaminosulph-on)-benzene with Na S in water and carbondisulp-hide, as described in Example 10.

Compound X VIlI.2-mercapto-5-(p-chloroanilino-suL phon)-benzthiazole are prepared from 1-chloro-2-nitro- (4-chloroanilinosulphon)-benzene, as described in Example X.

Compownd XIX-.2-mercapto S-carboxy-benzthiozole is prepared from 4-chloro-3-nitrobenzoicacid, as described in Example 10.

Compound XX .-t-2-mercapto-su1phonicacid-6,7benz0- benzthiozol is prepared by sulfonating 2n1ercapto-6,7 benzobenzthiazol with 20% oleurn at a temperature of 20. The reaction mixture is poured onto ice and precipitated with a saturated solution of sodium chloride.

Compound X XI .--2-rnercapto-su1phonicacid-benzothiazin is prepared as described in Example XX from Z-mercapto-benzothiazin.

Compound XXII .2-mercapto-5 -suiphonieacid benzselenazol is prepared from 1-chloro-2-nitro-4-benzenesulphonic acid with potassiumselenide and cyclisation with carbondisulphide, as described in Example X.

Compound XXlII.2-mercapto-5 carboxybenzselenazole is prepared as described for Compound XXII from 4-ch1oro-3-nitr0benzoicacid.

I-IOaS- \CSH HOBS N/ C-SH N HOaS CSH N VI HOaS CSH N HOsS VII /0 HO S- 3 CSH VIII 5031-1 C-SH CSH X II

XIII

XIV

XVI

XVII

XIX

XXI

XXII

HOOC

(IJOOH c H -s1r Hum-01s s H c-srr NO2S C-SH HOOC HOaS C-SH N s HOBS l o-sn XXIII /Se HH H000 We claim:

1. In a process for the production of photographic images by exposing a supported light-sensitive silver halide emulsion, developing and fixing the exposed layer, the improvement consisting in developing the exposed silver halide emulsion layer in effective contact with a stabilizing compound of the formula:

wherein Z stands for a bivalent atom selected from the group consisting of oxygen, sulfur and selenium and Y stands for the carbon atoms necessary for completing a ring selected from the group consisting of a -membered ring and a 6-membered ring, said rings being fused to an aryl ring selected from the group consisting of benzene and naphthalene, said aryl ring being substituted by a substituent selected from the group consisting of carboxyl, sulfonic acid and sulphonamide.

2. A light-sensitive material having at least one supported silver halide emulsion layer, containing a stabilizing compound of the formula:

wherein Z stands for a bivalent atom selected from the group consisting of oxygen, sulfur and selenium and Y stands for the carbon atoms necessary for completing a ring selected from the group consisting of a 5-membered ring and a 6-membered ring, said rings being fused to an aryl ring selected from the group consisting of benzene and naphthalene, said aryl ring being substituted by a substituent selected from the group consisting of carboxyl, sulfonic acid and sulphonamide.

3. An aqueous alkaline developing composition containing a developing amount of a silver halide developer and a stabilizing amount of a stabilizing compound of the formula:

wherein Z stands for a bivalent atom selected from the group consisting of oxygen, sulfur and selenium and Y stands for the carbon atoms necessary for completing a ring selected from the group consisting of a 5-membered ring and a 6-membered ring, said rings being fused to an aryl ring selected from the group consisting of benzene and naphthalene, said aryl ring being substituted by a substituent selected from the group consisting of carboxyl, sulfonic acid and sulphonamide.

4. A process as defined in claim 1 wherein Y stands for the ring members necessary to complete a heterocyclic ring selected from the group consisting of benzoxazole, naphthoxazole, benzthiazole, naphthothiazole, benzselenazole, benzsthiazine and naphthoxazine, said rings being substituted by substituents selected from the group consisting of carboxyl, sulfonic acid and sulfonamide.

5. The light-sensitive material according to claim 2 wherein Y stands for the ring members necessary to complete a heterocyclic ring selected from the group consisting of benzoxazole, naphthoxazole, benzthiazole,

10 naphthothiazole, benzselenazole, benzthiazine and naphthoxazine, said rings being substituted by substituents selected from the group consisting of carboxyl, sulfonic acid and sulfonamide.

6. The aqueous development mixture as defined in claim 3 wherein Y stands for the ring members necessary to complete a heterocyclic ring selected from the group consisting of benzoxazole, naphthoxazole, benzthiazole, naphthothiazole, benzselenazole, benzthiazine and naphthoxazine, said rings being substituted by substituents selected from the group consisting of carboxyl, sulfonic acid and sulfonamide.

7. The process as defined in claim 1 wherein the stabilizing compound has the formula:

o-sn

9. The process as defined in claim 1 wherein the stabilizing compound has the formula:

HOaS

10. The process as defi'n'ed in claim 1 wherein the stabilizing compound has the formula:

11. The process as defined in claim 1 wherein the stabilizing compound has the formula:

12. The light-sensitive material as defined in claim 2 wherein the stabilizing compound has the formula:

HOaS- I 13. The light-sensitive material as defined in claim 2 wherein 'the stabilizing compound has the formula:

o-sn HOaS% 14. The light-sensitive material as defined in claim 2 wherein the stabilizing compound has the formula:

HOaS

15. The light-sensitive material as defined in claim 2 wherein the stabilizing compound has the formula:

16. The light-sensitive material as defined in claim 2 wherein the stabilizing compound has the formula:

SOaH

17. The aqueous alkaline developing composition as defined in claim 3 wherein the stabilizing compound has the formula:

Ho=s C-SH 18. The aqueous alkaline developing composition as defined in claim 3 wherein the stabilizing compound has the formula:

19. The aqueous alkaline developing composition as defined in claim 3 wherein the stabilizing compound has the formula:

0 I IIOSS- 20. The aqueous alkaline developing composition as defined in claim 3 wherein the stabilizing compound has the formula:

C-SH

21. The aqueous alkaline developing composition as defined in claim 3 wherein the stabilizing compound has the formula:

NORMAN G. TORCHIN, Primary Examiner.

A. D. RICCI, Assistant Examiner. 

1. IN A PROCESS FOR THE PRODUCTION OF PHOTOGRAPHIC IMAGES BY EXPOSING A SUPPORTED LIGHT-SENSITIVE SILVER HALIDE EMULSION, DEVELOPING AND FIXING THE EXPOSED LAYER, THE IMPROVEMENT CONSISTING IN DEVELPING THE EXPOSED SILVER HALIDE EMULSION LAYER IN EFFECTIVE CONTACT WITH A STABILIZING COMPOUND OF THE FORMULA: 